Dependence of image flickering of negative dielectric anisotropy liquid crystal on the flexoelectric coefficient ratio and the interdigitated electrode structure

Lee, Hyojin; Kim, Hyung-Min; Kim, Jongyoon; Lee, Jihoon

doi:10.1088/0022-3727/49/7/075501

Cited by 16 publications

(10 citation statements)

References 23 publications

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“…The flexoelectric coefficients were set to e s ( e b ) = 0 (0) pC m −1 for the normal mode, and the ratio e s / e b = 0.5 for nLCs. It can be quite reasonable to consider averaging out two possible conformations for nematic liquid crystals: (1) an elongated shape with mostly trans conformation, e s / e b ∼ 1; (2) the most bent shape with a single gauche link in terminal chain, e s / e b = 0.2 (see Figure b,d). Adjustment of Δε and rotational viscosity γ 1 of liquid crystals is extrapolated by following the linear correlation between Δε and γ 1 .…”

Section: Resultsmentioning

confidence: 99%

Liquid Crystals for Superior Electro‐Optic Performance Display Device with Power‐Saving Mode

Kim

Jin

Lee

et al. 2018

Advanced Optical Materials

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for the additional power reduction in the liquid crystal driving scheme, for example, by reducing the driving frequency f. Displaying smooth and dynamic motion at high-frame rate has been an unquestionable direction to improve the performance of displays, but static images are also becoming significantly important as the application of displays diverges. Thus, as the f is in linear dependence on the power consumption of a module, low-f driving LCD is desired.In driving scheme of LCDs, some amount of electromagnetic radiant energy from the backlight is cut off by the combination of crossed polarizers and liquid crystalline medium while modulating polarization. In terms of energy loss in a liquid crystal layer, therefore, maximizing transmittance is an important factor to improve for better electro-optic performance. From this perspective, achieving both high optical transmittance and low-f driving would be a remarkable breakthrough in terms of power savings.There are two main streams of the initially homogeneous aligned light modulating mode in LCDs: fringe-field switching (FFS) and in-plane switching (IPS) modes. Both modes have a patterned electrode on the one side of two sandwiched substrates. In the IPS mode, patterned pixel (signal-swung) and common electrodes are interdigitated such that symmetrical lateral fields, which have the same translational periodicity with the electrode patterns, are formed between these two electrodes to rotating the liquid crystal director in plane; thus, reorientation occurs only in between the electrodes. In the FFS mode, on the other hand, a plain common electrode and a patterned pixel electrode are not on the same layer and separated by an insulation layer. With this structure, the electric fields form nonsymmetrical fringe shape and the field periodicity is half of the pitch of the electrode patterns. Thus, the rotation of the liquid crystal director takes place over the entire electrode area, which contributes more to the optical transmittance. [4,5] The FFS mode has been dominating the LCD market, especially in portable devices owing to the high aperture ratio, high transmittance, low operation voltage, wide-viewing angle, and touchscreen tolerance. [4,6] Consequently, intensive efforts to reduce the power consumption of this mode have been attempted by using the low-f driving when static images are being displayed. However, severe issues regarding image quality arise in the low-f driving, including image-flickering owing to flexoelectric effect. [7][8][9][10][11][12][13][14] The flexoelectric effect is a An advantageous factor for the technology of displays is low power consumption. For power-saving, low-frequency driving of liquid crystal displays (LCDs) is useful. However, an unacceptable performance drop, from image-flickering, occurs due to occurrence of the flexoelectric effect. Here, based on close agreement between experimental and simulated results, a new electro-optic mode with optimization of both electrode structures and physical properties of the liquid crystal...

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Section: Resultsmentioning

confidence: 99%

Liquid Crystals for Superior Electro‐Optic Performance Display Device with Power‐Saving Mode

Kim

Jin

Lee

et al. 2018

Advanced Optical Materials

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“…To investigate the image flickering phenomenon, we performed numerical calculation using a commercial simulation program, TechWiz LCD (Sanayi System Co., Korea). We investigated how the electrode spacing affects the image flickering phenomenon, with which we can examine the flexoelectric effect in an LC cell [9][10][11][12]. The LC parameters used for numerical calculations are as follows: the birefringence ǻn = 0.1029, the dielectric anisotropy ǻİ = 7.3, and the elastic constants K 11 = 12.6 pN, K 22 = 5.9 pN, and K 33 = 13 pN.…”

Section: Calculated Resultsmentioning

confidence: 99%

P-130: Investigation on Image Flicker in an FFS-LCD Panel: Dependence on Electrode Spacing

Park

Baek

et al. 2016

SID Symposium Digest of Technical Papers

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In case an LCD panel is driven by a low-frequency fringe field, image flickering phenomenon is detected by the naked human eye. We investigated the dependence on the electrode spacing of the image flickering phenomenon induced by the flexoelectric effect in an FFS LCD panel. We found that the image flicker in an FFS LCD panel under low-frequency driving can be eliminated in a simple manner by optimizing the electrode spacing. Author Keywords liquid crystal; fringe-field switching; flexoelectric effect; flicker P-130 / S.-W. Oh SID 2016 DIGEST • 1607 ISSN 0097-966X/16/4703-1607-$1.00

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“…There have been many approaches to enhance the flexoelectric effect of LC by doping bent-core LC or bimesogenic LC materials [5][6][7][8]. However, those materials generally have a poor miscibility with the nematic LC and have high temperature range of LC phase.…”

Section: Objective and Backgroundmentioning

confidence: 99%

P‐154: Increase of flexoelectric anisotropy of nematic liquid crystal doped with calamitic ferroelectric liquid crystal

Park

Kim

Lee

2019

Symp Digest of Tech Papers

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We report an increase of flexoelectric anisotropy (Δ ) of nematic liquid crystal by doping a calamitic ferroelectric liquid crystal (FLC). We tested two kinds of FLC and both nematic liquid crystal mixtures doped with each FLC showed an increase of the flexoelectric anisotropy up to 52%. The reason for the increase in flexoelectric anisotropy is thought to be due to the large transverse dipole moment of the FLC.Author Keywords flexoelectric effect, flexoelectric anisotropy, ferroelectric liquid crystal, chiral flexoelectro-optic method.

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Dependence of image flickering of negative dielectric anisotropy liquid crystal on the flexoelectric coefficient ratio and the interdigitated electrode structure

Cited by 16 publications

References 23 publications

Liquid Crystals for Superior Electro‐Optic Performance Display Device with Power‐Saving Mode

Liquid Crystals for Superior Electro‐Optic Performance Display Device with Power‐Saving Mode

P-130: Investigation on Image Flicker in an FFS-LCD Panel: Dependence on Electrode Spacing

P‐154: Increase of flexoelectric anisotropy of nematic liquid crystal doped with calamitic ferroelectric liquid crystal

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